In recent years, reduction in the size of and increase in the performance of electronic apparatuses have been progressing rapidly. Moreover, increase in transmission speed and reduction in drive voltage have been progressing rapidly as typically seen in high-speed transmission systems, such as USB 2.0, S-ATA 2, and HDMI. On the other hand, as reduction in the size of and reduction in the drive voltage of electronic apparatuses progress, the withstand voltages of electronic components used in the electronic apparatuses decrease. Therefore, it is technically important to protect electronic components from overvoltage, which is typified by an electrostatic pulse that occurs when a human body comes into contact with a terminal of an electronic apparatus.
To date, as protective measures against such an electrostatic pulse, a method of providing an antistatic component, such as a varistor, at a position between the ground and a line into which static electricity flows has been used. Because the frequency of signals has higher frequency in recent years, the quality of signals decreases if the antistatic component described above has a high capacitance. Therefore, it is necessary to use an antistatic component having a capacitance of 1 pF or less when the transmission speed is several hundred Mbps or higher. Moreover, it has been not been possible to use an electrostatic protection component having a high capacitance in an antenna circuit or an RF module.
Low-capacity antistatic components have been proposed in which a space between opposing electrodes is filled with an electrostatic protection material. For example, PTL 1 discloses an antistatic device in which a pair of electrodes are disposed opposite each other on an insulating substrate and a gap between the electrodes is covered with an overvoltage protection material layer.
PTL 2 discloses an antistatic device in which a composite portion is disposed between opposing portions of discharge electrodes and a ceramic multilayer substrate. The composite portion is made of a material including a metallic material and a ceramic material. The shrinkage of the metallic substrate when being fired is identical or similar to that of the opposing portions of the discharge electrodes. The shrinkage of the ceramic substrate when being fired is identical or similar to that of the material of the ceramic multilayer substrate.